Selection of rolling bearings

Published on:

2022-07-28 16:23

  1. Bearing capacity
  We mentioned earlier that rolling bearings can be divided into ball bearings and roller bearings. The classification is based on the different shapes of rolling elements.
Generally speaking, under the same overall dimensions, the bearing capacity of roller bearings is 1.5-3 times that of ball bearings, so when there is a large load or impact load, we can give priority to roller bearings.
However, when the diameter is less than or equal to 20mm, the bearing capacity of the two is not much different, and the price of ball bearings is cheaper than roller bearings, so we give priority to ball bearings.
  2. The speed cannot exceed the limit speed
  Too high speed of rolling bearings will increase the temperature between friction surfaces, resulting in high temperature. In this case, the lubrication of the two metal surfaces fails, and the rolling will cause bonding failure.
Gluing phenomenon: the two surfaces in contact will stick together. Due to relative sliding at this time, the bonded part may be torn, and then scars will be formed on the surface along the sliding direction.
We call the maximum allowable speed of a rolling bearing under certain load and lubrication conditions as the limit speed.
In the design, if the speed of the rotating shaft is known, when selecting the rolling bearing, we should make its limit speed greater than the speed of the shaft, so that the rolling bearing is safe.
The limit speed of rolling bearings can be found in the mechanical design manual.
  3. Allowable range of angular deviation
  The central line of the inner and outer rings of the bearing will be relatively inclined due to incorrect installation or shaft deformation. The angle of inclination is called angular deviation.
If the angular deviation is too large, it can even affect the normal operation of the shaft. At this time, you can choose self-aligning bearings, such as self-aligning ball bearings or self-aligning roller bearings.
The outer race of self-aligning bearing is a spherical surface centered on the bearing center, so it can be self-aligning.
Angular deviation is not allowed for thrust ball bearings and needle roller bearings.
The thrust ball bearing can only bear axial load, and the action line in the load direction must coincide with the axis.
If there is angular deviation, the thrust ball bearing will be seriously damaged.
The rolling element of needle roller bearing is in line contact with the outer ring, which is most sensitive to axis deflection. It should be avoided to use in the case of axis deflection.
  4. Angular contact radial bearings should exist in pairs and cannot exist alone
  Here, angular contact radial bearings generally refer to tapered roller bearings and angular contact ball bearings.
When the shaft is in contact with the bearing, the angular contact radial bearing will generate additional axial force due to the existence of contact angle when bearing radial load, so it is generally used in pairs.
There are two ways of installation: front installation and reverse installation.
The front installation means that the narrow edges of the two outer rings are opposite, and the reverse installation means that the wide edges of the two outer rings are opposite.
  5. Lubrication mode
  The lubricant of rolling bearings can be grease, lubricating oil, or solid lubricant.
Generally, rolling bearings are lubricated with grease.
Grease lubrication is easy to seal and maintain because the grease is not easy to lose, and it can run for a long time after filling the grease at one time.
The advantage of oil lubrication is that it has less friction resistance than grease lubrication and can dissipate heat. It is mainly used for bearings with high speed or high working temperature.

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Website of Suzhou Dongwu Needle Roller Bearing Co., Ltd.

Suzhou Dongwu Needle Roller Bearing Co., Ltd. is located in Suzhou Industrial Park, adjacent to Wusong River and airport road in the south, national highway 312 and Shanghai Nanjing Expressway in the north, with superior geographical location and convenient transportation.